"There is always a bit of frustration when you feel like you are knocking on the door for a long time," Wenger said. "It is reassuring that we came through it tonight."
In the first match after the firing of manager John Hackworth, the Union had plenty of chances that were stifled by the outstanding play of Sylvestre, who couldn't be blamed for Wenger's first goal.
The 6-4 Sylvestre recorded 10 saves and came off the line well to break up crosses.
"He was very good," Union interim manager Jim Curtin said of Sylvestre. "When you walk out through the tunnel and you look at the kid, I looked up to him, so he is a big boy. He make some saves. Sometimes guys that are that size aren't as nimble. He was pretty quick to get to some things tonight that were special. He had a very good day."
The Union trailed for 50 minutes of the game against their affiliate, who were down five starters, including a goalkeeper, for the match. Danny DiPrima found Jason Pelletier in the box, who buried a goal to give the Islanders a lead they would hold for most of the match. The Union did not look crisp passing the ball when trying to equalize, and did not take advantage of opportunities against a team they should have easily beaten.
"A lot of times, these games wind up looking like this," Curtin said. "It is not the way you draw it up. You can warn the group as much as possible, but these games are always fights. I would like to give credit to Harrisburg, who was very undermanned tonight. They were missing a lot of players and put up a good fight.
"They had us on the ropes, to be honest. They had us frustrated. Fortunately, we were able to push it in during extra time and wear them out."
The Union tied the game at 1-all in the 89th minute, when Maurice Edu took a pass from Sebastien Le Toux and placed it in the back of the net. It was Edu's first game returning to the center back position, which is an option that Philadelphia is leaving open for now.
"He said for a couple games and we'll see how it goes," Edu said. "Regardless of where I'm playing I am just trying to help the team win."
The Union move on to the fifth round of the U.S. Open Cup and take on the New York Cosmos on Tuesday night at PPL Park.